Hydrogels are water-swollen networks of hydrophilic homopolymers or copolymers. These networks may be formed by various techniques; however, the most common synthetic route is the free radical polymerization of vinyl monomers in the presence of a difunctional cross-linking agent and a swelling agent. The resulting polymer exhibits both liquid-like properties, attributable to the major constituent, water, and solid-like properties due to the network formed by the cross-linking reaction. These solid-like properties take the form of a shear modulus that is evident upon deformation.
Hydrogels offer biocompatibility and have been shown to have reduced tendency for inducing thrombosis, encrustation and inflammation when used in medical devices. Unfortunately, the use of hydrogels in biomedical device applications has been hindered by poor mechanical performance. Many medical devices use hydrogels to improve device biocompatibility; however, many hydrogels can only be used in coatings as a result of insufficient mechanical performance for use as a bulk polymer. Many hydrogels suffer from low modulus, low yield stress, and low strength when compared to non-swollen polymer systems. Lower mechanical properties result from the swollen nature of hydrogels and the non-stress bearing nature of the swelling agent.
The state of the art hydrogel formulations do not adequately bind to all types of tissue surfaces. Furthermore, many of the existing hydrogel materials are not consistent in their ability to provide hemostatic control. The potency of these materials is limited by addressing one of the many qualities that are desirable in a hydrogel biomaterial (e.g. hemostasis or acting as an adhesion barrier, or providing infection control, or eliciting a minimal tissue response). A hydrogel biomaterial that addresses these multiple qualities consistently is not currently available in the art.
As such, there is a continuing need to develop new compositions capable of forming biocompatible hydrogel structures that offer improved therapeutic outcomes.